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                  <h1>underscore.js</h1>
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              <pre><code>Underscore.js <span class="hljs-number">1.9</span><span class="hljs-number">.2</span>
https:<span class="hljs-comment">//underscorejs.org</span>
(c) <span class="hljs-number">2009</span><span class="hljs-number">-2018</span> Jeremy Ashkenas, DocumentCloud and Investigative Reporters &amp; Editors
Underscore may be freely distributed under the MIT license.
</code></pre>
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            <div class="content"><div class='highlight'><pre>
(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{</pre></div></div>
            
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              <h2 id="baseline-setup">Baseline setup</h2>

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              <p>Establish the root object, <code>window</code> (<code>self</code>) in the browser, <code>global</code>
on the server, or <code>this</code> in some virtual machines. We use <code>self</code>
instead of <code>window</code> for <code>WebWorker</code> support.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> root = <span class="hljs-keyword">typeof</span> self == <span class="hljs-string">'object'</span> &amp;&amp; self.self === self &amp;&amp; self ||
            <span class="hljs-keyword">typeof</span> global == <span class="hljs-string">'object'</span> &amp;&amp; global.global === global &amp;&amp; global ||
            <span class="hljs-keyword">this</span> ||
            {};</pre></div></div>
            
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              <p>Save the previous value of the <code>_</code> variable.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> previousUnderscore = root._;</pre></div></div>
            
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              <p>Save bytes in the minified (but not gzipped) version:</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> ArrayProto = <span class="hljs-built_in">Array</span>.prototype, ObjProto = <span class="hljs-built_in">Object</span>.prototype;
  <span class="hljs-keyword">var</span> SymbolProto = <span class="hljs-keyword">typeof</span> <span class="hljs-built_in">Symbol</span> !== <span class="hljs-string">'undefined'</span> ? <span class="hljs-built_in">Symbol</span>.prototype : <span class="hljs-literal">null</span>;</pre></div></div>
            
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              <p>Create quick reference variables for speed access to core prototypes.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> push = ArrayProto.push,
      slice = ArrayProto.slice,
      toString = ObjProto.toString,
      hasOwnProperty = ObjProto.hasOwnProperty;</pre></div></div>
            
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              <p>All <strong>ECMAScript 5</strong> native function implementations that we hope to use
are declared here.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> nativeIsArray = <span class="hljs-built_in">Array</span>.isArray,
      nativeKeys = <span class="hljs-built_in">Object</span>.keys,
      nativeCreate = <span class="hljs-built_in">Object</span>.create;</pre></div></div>
            
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              <p>Naked function reference for surrogate-prototype-swapping.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> Ctor = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>)</span>{};</pre></div></div>
            
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              <p>Create a safe reference to the Underscore object for use below.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> _ = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">if</span> (obj <span class="hljs-keyword">instanceof</span> _) <span class="hljs-keyword">return</span> obj;
    <span class="hljs-keyword">if</span> (!(<span class="hljs-keyword">this</span> <span class="hljs-keyword">instanceof</span> _)) <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> _(obj);
    <span class="hljs-keyword">this</span>._wrapped = obj;
  };</pre></div></div>
            
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              <p>Export the Underscore object for <strong>Node.js</strong>, with
backwards-compatibility for their old module API. If we’re in
the browser, add <code>_</code> as a global object.
(<code>nodeType</code> is checked to ensure that <code>module</code>
and <code>exports</code> are not HTML elements.)</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> exports != <span class="hljs-string">'undefined'</span> &amp;&amp; !exports.nodeType) {
    <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> <span class="hljs-built_in">module</span> != <span class="hljs-string">'undefined'</span> &amp;&amp; !<span class="hljs-built_in">module</span>.nodeType &amp;&amp; <span class="hljs-built_in">module</span>.exports) {
      exports = <span class="hljs-built_in">module</span>.exports = _;
    }
    exports._ = _;
  } <span class="hljs-keyword">else</span> {
    root._ = _;
  }</pre></div></div>
            
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              <p>Current version.</p>

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            <div class="content"><div class='highlight'><pre>  _.VERSION = <span class="hljs-string">'1.9.2'</span>;</pre></div></div>
            
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              <p>Internal function that returns an efficient (for current engines) version
of the passed-in callback, to be repeatedly applied in other Underscore
functions.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> optimizeCb = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, context, argCount</span>) </span>{
    <span class="hljs-keyword">if</span> (context === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>) <span class="hljs-keyword">return</span> func;
    <span class="hljs-keyword">switch</span> (argCount == <span class="hljs-literal">null</span> ? <span class="hljs-number">3</span> : argCount) {
      <span class="hljs-keyword">case</span> <span class="hljs-number">1</span>: <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value</span>) </span>{
        <span class="hljs-keyword">return</span> func.call(context, value);
      };</pre></div></div>
            
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              <p>The 2-argument case is omitted because we’re not using it.</p>

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            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">case</span> <span class="hljs-number">3</span>: <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value, index, collection</span>) </span>{
        <span class="hljs-keyword">return</span> func.call(context, value, index, collection);
      };
      <span class="hljs-keyword">case</span> <span class="hljs-number">4</span>: <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">accumulator, value, index, collection</span>) </span>{
        <span class="hljs-keyword">return</span> func.call(context, accumulator, value, index, collection);
      };
    }
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">return</span> func.apply(context, <span class="hljs-built_in">arguments</span>);
    };
  };

  <span class="hljs-keyword">var</span> builtinIteratee;</pre></div></div>
            
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              <p>An internal function to generate callbacks that can be applied to each
element in a collection, returning the desired result — either <code>identity</code>,
an arbitrary callback, a property matcher, or a property accessor.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> cb = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value, context, argCount</span>) </span>{
    <span class="hljs-keyword">if</span> (_.iteratee !== builtinIteratee) <span class="hljs-keyword">return</span> _.iteratee(value, context);
    <span class="hljs-keyword">if</span> (value == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> _.identity;
    <span class="hljs-keyword">if</span> (_.isFunction(value)) <span class="hljs-keyword">return</span> optimizeCb(value, context, argCount);
    <span class="hljs-keyword">if</span> (_.isObject(value) &amp;&amp; !_.isArray(value)) <span class="hljs-keyword">return</span> _.matcher(value);
    <span class="hljs-keyword">return</span> _.property(value);
  };</pre></div></div>
            
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              <p>External wrapper for our callback generator. Users may customize
<code>_.iteratee</code> if they want additional predicate/iteratee shorthand styles.
This abstraction hides the internal-only argCount argument.</p>

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            <div class="content"><div class='highlight'><pre>  _.iteratee = builtinIteratee = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value, context</span>) </span>{
    <span class="hljs-keyword">return</span> cb(value, context, <span class="hljs-literal">Infinity</span>);
  };</pre></div></div>
            
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              <p>Some functions take a variable number of arguments, or a few expected
arguments at the beginning and then a variable number of values to operate
on. This helper accumulates all remaining arguments past the function’s
argument length (or an explicit <code>startIndex</code>), into an array that becomes
the last argument. Similar to ES6’s “rest parameter”.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> restArguments = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, startIndex</span>) </span>{
    startIndex = startIndex == <span class="hljs-literal">null</span> ? func.length - <span class="hljs-number">1</span> : +startIndex;
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">var</span> length = <span class="hljs-built_in">Math</span>.max(<span class="hljs-built_in">arguments</span>.length - startIndex, <span class="hljs-number">0</span>),
          rest = <span class="hljs-built_in">Array</span>(length),
          index = <span class="hljs-number">0</span>;
      <span class="hljs-keyword">for</span> (; index &lt; length; index++) {
        rest[index] = <span class="hljs-built_in">arguments</span>[index + startIndex];
      }
      <span class="hljs-keyword">switch</span> (startIndex) {
        <span class="hljs-keyword">case</span> <span class="hljs-number">0</span>: <span class="hljs-keyword">return</span> func.call(<span class="hljs-keyword">this</span>, rest);
        <span class="hljs-keyword">case</span> <span class="hljs-number">1</span>: <span class="hljs-keyword">return</span> func.call(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>[<span class="hljs-number">0</span>], rest);
        <span class="hljs-keyword">case</span> <span class="hljs-number">2</span>: <span class="hljs-keyword">return</span> func.call(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>[<span class="hljs-number">0</span>], <span class="hljs-built_in">arguments</span>[<span class="hljs-number">1</span>], rest);
      }
      <span class="hljs-keyword">var</span> args = <span class="hljs-built_in">Array</span>(startIndex + <span class="hljs-number">1</span>);
      <span class="hljs-keyword">for</span> (index = <span class="hljs-number">0</span>; index &lt; startIndex; index++) {
        args[index] = <span class="hljs-built_in">arguments</span>[index];
      }
      args[startIndex] = rest;
      <span class="hljs-keyword">return</span> func.apply(<span class="hljs-keyword">this</span>, args);
    };
  };</pre></div></div>
            
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              <p>An internal function for creating a new object that inherits from another.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> baseCreate = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">prototype</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isObject(prototype)) <span class="hljs-keyword">return</span> {};
    <span class="hljs-keyword">if</span> (nativeCreate) <span class="hljs-keyword">return</span> nativeCreate(prototype);
    Ctor.prototype = prototype;
    <span class="hljs-keyword">var</span> result = <span class="hljs-keyword">new</span> Ctor;
    Ctor.prototype = <span class="hljs-literal">null</span>;
    <span class="hljs-keyword">return</span> result;
  };

  <span class="hljs-keyword">var</span> shallowProperty = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">key</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
      <span class="hljs-keyword">return</span> obj == <span class="hljs-literal">null</span> ? <span class="hljs-keyword">void</span> <span class="hljs-number">0</span> : obj[key];
    };
  };

  <span class="hljs-keyword">var</span> has = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, path</span>) </span>{
    <span class="hljs-keyword">return</span> obj != <span class="hljs-literal">null</span> &amp;&amp; hasOwnProperty.call(obj, path);
  }

  <span class="hljs-keyword">var</span> deepGet = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, path</span>) </span>{
    <span class="hljs-keyword">var</span> length = path.length;
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; length; i++) {
      <span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>;
      obj = obj[path[i]];
    }
    <span class="hljs-keyword">return</span> length ? obj : <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>;
  };</pre></div></div>
            
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              <p>Helper for collection methods to determine whether a collection
should be iterated as an array or as an object.
Related: <a href="https://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength">https://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength</a>
Avoids a very nasty iOS 8 JIT bug on ARM-64. #2094</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> MAX_ARRAY_INDEX = <span class="hljs-built_in">Math</span>.pow(<span class="hljs-number">2</span>, <span class="hljs-number">53</span>) - <span class="hljs-number">1</span>;
  <span class="hljs-keyword">var</span> getLength = shallowProperty(<span class="hljs-string">'length'</span>);
  <span class="hljs-keyword">var</span> isArrayLike = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">collection</span>) </span>{
    <span class="hljs-keyword">var</span> length = getLength(collection);
    <span class="hljs-keyword">return</span> <span class="hljs-keyword">typeof</span> length == <span class="hljs-string">'number'</span> &amp;&amp; length &gt;= <span class="hljs-number">0</span> &amp;&amp; length &lt;= MAX_ARRAY_INDEX;
  };</pre></div></div>
            
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              <h2 id="collection-functions">Collection Functions</h2>

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              <p>The cornerstone, an <code>each</code> implementation, aka <code>forEach</code>.
Handles raw objects in addition to array-likes. Treats all
sparse array-likes as if they were dense.</p>

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            <div class="content"><div class='highlight'><pre>  _.each = _.forEach = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, context</span>) </span>{
    iteratee = optimizeCb(iteratee, context);
    <span class="hljs-keyword">var</span> i, length;
    <span class="hljs-keyword">if</span> (isArrayLike(obj)) {
      <span class="hljs-keyword">for</span> (i = <span class="hljs-number">0</span>, length = obj.length; i &lt; length; i++) {
        iteratee(obj[i], i, obj);
      }
    } <span class="hljs-keyword">else</span> {
      <span class="hljs-keyword">var</span> keys = _.keys(obj);
      <span class="hljs-keyword">for</span> (i = <span class="hljs-number">0</span>, length = keys.length; i &lt; length; i++) {
        iteratee(obj[keys[i]], keys[i], obj);
      }
    }
    <span class="hljs-keyword">return</span> obj;
  };</pre></div></div>
            
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              <p>Return the results of applying the iteratee to each element.</p>

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            <div class="content"><div class='highlight'><pre>  _.map = _.collect = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, context</span>) </span>{
    iteratee = cb(iteratee, context);
    <span class="hljs-keyword">var</span> keys = !isArrayLike(obj) &amp;&amp; _.keys(obj),
        length = (keys || obj).length,
        results = <span class="hljs-built_in">Array</span>(length);
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>; index &lt; length; index++) {
      <span class="hljs-keyword">var</span> currentKey = keys ? keys[index] : index;
      results[index] = iteratee(obj[currentKey], currentKey, obj);
    }
    <span class="hljs-keyword">return</span> results;
  };</pre></div></div>
            
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              <p>Create a reducing function iterating left or right.</p>

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            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> createReduce = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">dir</span>) </span>{</pre></div></div>
            
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              <p>Wrap code that reassigns argument variables in a separate function than
the one that accesses <code>arguments.length</code> to avoid a perf hit. (#1991)</p>

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            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">var</span> reducer = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, memo, initial</span>) </span>{
      <span class="hljs-keyword">var</span> keys = !isArrayLike(obj) &amp;&amp; _.keys(obj),
          length = (keys || obj).length,
          index = dir &gt; <span class="hljs-number">0</span> ? <span class="hljs-number">0</span> : length - <span class="hljs-number">1</span>;
      <span class="hljs-keyword">if</span> (!initial) {
        memo = obj[keys ? keys[index] : index];
        index += dir;
      }
      <span class="hljs-keyword">for</span> (; index &gt;= <span class="hljs-number">0</span> &amp;&amp; index &lt; length; index += dir) {
        <span class="hljs-keyword">var</span> currentKey = keys ? keys[index] : index;
        memo = iteratee(memo, obj[currentKey], currentKey, obj);
      }
      <span class="hljs-keyword">return</span> memo;
    };

    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, memo, context</span>) </span>{
      <span class="hljs-keyword">var</span> initial = <span class="hljs-built_in">arguments</span>.length &gt;= <span class="hljs-number">3</span>;
      <span class="hljs-keyword">return</span> reducer(obj, optimizeCb(iteratee, context, <span class="hljs-number">4</span>), memo, initial);
    };
  };</pre></div></div>
            
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              <p><strong>Reduce</strong> builds up a single result from a list of values, aka <code>inject</code>,
or <code>foldl</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.reduce = _.foldl = _.inject = createReduce(<span class="hljs-number">1</span>);</pre></div></div>
            
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              <p>The right-associative version of reduce, also known as <code>foldr</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.reduceRight = _.foldr = createReduce(<span class="hljs-number">-1</span>);</pre></div></div>
            
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              <p>Return the first value which passes a truth test. Aliased as <code>detect</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.find = _.detect = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, predicate, context</span>) </span>{
    <span class="hljs-keyword">var</span> keyFinder = isArrayLike(obj) ? _.findIndex : _.findKey;
    <span class="hljs-keyword">var</span> key = keyFinder(obj, predicate, context);
    <span class="hljs-keyword">if</span> (key !== <span class="hljs-keyword">void</span> <span class="hljs-number">0</span> &amp;&amp; key !== <span class="hljs-number">-1</span>) <span class="hljs-keyword">return</span> obj[key];
  };</pre></div></div>
            
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              <p>Return all the elements that pass a truth test.
Aliased as <code>select</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.filter = _.select = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, predicate, context</span>) </span>{
    <span class="hljs-keyword">var</span> results = [];
    predicate = cb(predicate, context);
    _.each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value, index, list</span>) </span>{
      <span class="hljs-keyword">if</span> (predicate(value, index, list)) results.push(value);
    });
    <span class="hljs-keyword">return</span> results;
  };</pre></div></div>
            
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              <p>Return all the elements for which a truth test fails.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.reject = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, predicate, context</span>) </span>{
    <span class="hljs-keyword">return</span> _.filter(obj, _.negate(cb(predicate)), context);
  };</pre></div></div>
            
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              <p>Determine whether all of the elements match a truth test.
Aliased as <code>all</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.every = _.all = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, predicate, context</span>) </span>{
    predicate = cb(predicate, context);
    <span class="hljs-keyword">var</span> keys = !isArrayLike(obj) &amp;&amp; _.keys(obj),
        length = (keys || obj).length;
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>; index &lt; length; index++) {
      <span class="hljs-keyword">var</span> currentKey = keys ? keys[index] : index;
      <span class="hljs-keyword">if</span> (!predicate(obj[currentKey], currentKey, obj)) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
    }
    <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
  };</pre></div></div>
            
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              <p>Determine if at least one element in the object matches a truth test.
Aliased as <code>any</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.some = _.any = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, predicate, context</span>) </span>{
    predicate = cb(predicate, context);
    <span class="hljs-keyword">var</span> keys = !isArrayLike(obj) &amp;&amp; _.keys(obj),
        length = (keys || obj).length;
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>; index &lt; length; index++) {
      <span class="hljs-keyword">var</span> currentKey = keys ? keys[index] : index;
      <span class="hljs-keyword">if</span> (predicate(obj[currentKey], currentKey, obj)) <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
    }
    <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
  };</pre></div></div>
            
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              <p>Determine if the array or object contains a given item (using <code>===</code>).
Aliased as <code>includes</code> and <code>include</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.contains = _.includes = _.include = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, item, fromIndex, guard</span>) </span>{
    <span class="hljs-keyword">if</span> (!isArrayLike(obj)) obj = _.values(obj);
    <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> fromIndex != <span class="hljs-string">'number'</span> || guard) fromIndex = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">return</span> _.indexOf(obj, item, fromIndex) &gt;= <span class="hljs-number">0</span>;
  };</pre></div></div>
            
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              <p>Invoke a method (with arguments) on every item in a collection.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.invoke = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, path, args</span>) </span>{
    <span class="hljs-keyword">var</span> contextPath, func;
    <span class="hljs-keyword">if</span> (_.isFunction(path)) {
      func = path;
    } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (_.isArray(path)) {
      contextPath = path.slice(<span class="hljs-number">0</span>, <span class="hljs-number">-1</span>);
      path = path[path.length - <span class="hljs-number">1</span>];
    }
    <span class="hljs-keyword">return</span> _.map(obj, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">context</span>) </span>{
      <span class="hljs-keyword">var</span> method = func;
      <span class="hljs-keyword">if</span> (!method) {
        <span class="hljs-keyword">if</span> (contextPath &amp;&amp; contextPath.length) {
          context = deepGet(context, contextPath);
        }
        <span class="hljs-keyword">if</span> (context == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>;
        method = context[path];
      }
      <span class="hljs-keyword">return</span> method == <span class="hljs-literal">null</span> ? method : method.apply(context, args);
    });
  });</pre></div></div>
            
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              <p>Convenience version of a common use case of <code>map</code>: fetching a property.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.pluck = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, key</span>) </span>{
    <span class="hljs-keyword">return</span> _.map(obj, _.property(key));
  };</pre></div></div>
            
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              <p>Convenience version of a common use case of <code>filter</code>: selecting only objects
containing specific <code>key:value</code> pairs.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.where = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, attrs</span>) </span>{
    <span class="hljs-keyword">return</span> _.filter(obj, _.matcher(attrs));
  };</pre></div></div>
            
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              <p>Convenience version of a common use case of <code>find</code>: getting the first object
containing specific <code>key:value</code> pairs.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.findWhere = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, attrs</span>) </span>{
    <span class="hljs-keyword">return</span> _.find(obj, _.matcher(attrs));
  };</pre></div></div>
            
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              <p>Return the maximum element (or element-based computation).</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.max = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, context</span>) </span>{
    <span class="hljs-keyword">var</span> result = -<span class="hljs-literal">Infinity</span>, lastComputed = -<span class="hljs-literal">Infinity</span>,
        value, computed;
    <span class="hljs-keyword">if</span> (iteratee == <span class="hljs-literal">null</span> || <span class="hljs-keyword">typeof</span> iteratee == <span class="hljs-string">'number'</span> &amp;&amp; <span class="hljs-keyword">typeof</span> obj[<span class="hljs-number">0</span>] != <span class="hljs-string">'object'</span> &amp;&amp; obj != <span class="hljs-literal">null</span>) {
      obj = isArrayLike(obj) ? obj : _.values(obj);
      <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = obj.length; i &lt; length; i++) {
        value = obj[i];
        <span class="hljs-keyword">if</span> (value != <span class="hljs-literal">null</span> &amp;&amp; value &gt; result) {
          result = value;
        }
      }
    } <span class="hljs-keyword">else</span> {
      iteratee = cb(iteratee, context);
      _.each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">v, index, list</span>) </span>{
        computed = iteratee(v, index, list);
        <span class="hljs-keyword">if</span> (computed &gt; lastComputed || computed === -<span class="hljs-literal">Infinity</span> &amp;&amp; result === -<span class="hljs-literal">Infinity</span>) {
          result = v;
          lastComputed = computed;
        }
      });
    }
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              <p>Return the minimum element (or element-based computation).</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.min = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, context</span>) </span>{
    <span class="hljs-keyword">var</span> result = <span class="hljs-literal">Infinity</span>, lastComputed = <span class="hljs-literal">Infinity</span>,
        value, computed;
    <span class="hljs-keyword">if</span> (iteratee == <span class="hljs-literal">null</span> || <span class="hljs-keyword">typeof</span> iteratee == <span class="hljs-string">'number'</span> &amp;&amp; <span class="hljs-keyword">typeof</span> obj[<span class="hljs-number">0</span>] != <span class="hljs-string">'object'</span> &amp;&amp; obj != <span class="hljs-literal">null</span>) {
      obj = isArrayLike(obj) ? obj : _.values(obj);
      <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = obj.length; i &lt; length; i++) {
        value = obj[i];
        <span class="hljs-keyword">if</span> (value != <span class="hljs-literal">null</span> &amp;&amp; value &lt; result) {
          result = value;
        }
      }
    } <span class="hljs-keyword">else</span> {
      iteratee = cb(iteratee, context);
      _.each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">v, index, list</span>) </span>{
        computed = iteratee(v, index, list);
        <span class="hljs-keyword">if</span> (computed &lt; lastComputed || computed === <span class="hljs-literal">Infinity</span> &amp;&amp; result === <span class="hljs-literal">Infinity</span>) {
          result = v;
          lastComputed = computed;
        }
      });
    }
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              <p>Shuffle a collection.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.shuffle = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">return</span> _.sample(obj, <span class="hljs-literal">Infinity</span>);
  };</pre></div></div>
            
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              <p>Sample <strong>n</strong> random values from a collection using the modern version of the
<a href="https://en.wikipedia.org/wiki/Fisher–Yates_shuffle">Fisher-Yates shuffle</a>.
If <strong>n</strong> is not specified, returns a single random element.
The internal <code>guard</code> argument allows it to work with <code>map</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.sample = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, n, guard</span>) </span>{
    <span class="hljs-keyword">if</span> (n == <span class="hljs-literal">null</span> || guard) {
      <span class="hljs-keyword">if</span> (!isArrayLike(obj)) obj = _.values(obj);
      <span class="hljs-keyword">return</span> obj[_.random(obj.length - <span class="hljs-number">1</span>)];
    }
    <span class="hljs-keyword">var</span> sample = isArrayLike(obj) ? _.clone(obj) : _.values(obj);
    <span class="hljs-keyword">var</span> length = getLength(sample);
    n = <span class="hljs-built_in">Math</span>.max(<span class="hljs-built_in">Math</span>.min(n, length), <span class="hljs-number">0</span>);
    <span class="hljs-keyword">var</span> last = length - <span class="hljs-number">1</span>;
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>; index &lt; n; index++) {
      <span class="hljs-keyword">var</span> rand = _.random(index, last);
      <span class="hljs-keyword">var</span> temp = sample[index];
      sample[index] = sample[rand];
      sample[rand] = temp;
    }
    <span class="hljs-keyword">return</span> sample.slice(<span class="hljs-number">0</span>, n);
  };</pre></div></div>
            
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              <p>Sort the object’s values by a criterion produced by an iteratee.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.sortBy = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, context</span>) </span>{
    <span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>;
    iteratee = cb(iteratee, context);
    <span class="hljs-keyword">return</span> _.pluck(_.map(obj, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value, key, list</span>) </span>{
      <span class="hljs-keyword">return</span> {
        <span class="hljs-attr">value</span>: value,
        <span class="hljs-attr">index</span>: index++,
        <span class="hljs-attr">criteria</span>: iteratee(value, key, list)
      };
    }).sort(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">left, right</span>) </span>{
      <span class="hljs-keyword">var</span> a = left.criteria;
      <span class="hljs-keyword">var</span> b = right.criteria;
      <span class="hljs-keyword">if</span> (a !== b) {
        <span class="hljs-keyword">if</span> (a &gt; b || a === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>) <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>;
        <span class="hljs-keyword">if</span> (a &lt; b || b === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>) <span class="hljs-keyword">return</span> <span class="hljs-number">-1</span>;
      }
      <span class="hljs-keyword">return</span> left.index - right.index;
    }), <span class="hljs-string">'value'</span>);
  };</pre></div></div>
            
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              <p>An internal function used for aggregate “group by” operations.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> group = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">behavior, partition</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, context</span>) </span>{
      <span class="hljs-keyword">var</span> result = partition ? [[], []] : {};
      iteratee = cb(iteratee, context);
      _.each(obj, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value, index</span>) </span>{
        <span class="hljs-keyword">var</span> key = iteratee(value, index, obj);
        behavior(result, value, key);
      });
      <span class="hljs-keyword">return</span> result;
    };
  };</pre></div></div>
            
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              <p>Groups the object’s values by a criterion. Pass either a string attribute
to group by, or a function that returns the criterion.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.groupBy = group(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">result, value, key</span>) </span>{
    <span class="hljs-keyword">if</span> (has(result, key)) result[key].push(value); <span class="hljs-keyword">else</span> result[key] = [value];
  });</pre></div></div>
            
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              <p>Indexes the object’s values by a criterion, similar to <code>groupBy</code>, but for
when you know that your index values will be unique.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.indexBy = group(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">result, value, key</span>) </span>{
    result[key] = value;
  });</pre></div></div>
            
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              <p>Counts instances of an object that group by a certain criterion. Pass
either a string attribute to count by, or a function that returns the
criterion.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.countBy = group(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">result, value, key</span>) </span>{
    <span class="hljs-keyword">if</span> (has(result, key)) result[key]++; <span class="hljs-keyword">else</span> result[key] = <span class="hljs-number">1</span>;
  });

  <span class="hljs-keyword">var</span> reStrSymbol = <span class="hljs-regexp">/[^\ud800-\udfff]|[\ud800-\udbff][\udc00-\udfff]|[\ud800-\udfff]/g</span>;</pre></div></div>
            
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              <p>Safely create a real, live array from anything iterable.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.toArray = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">if</span> (!obj) <span class="hljs-keyword">return</span> [];
    <span class="hljs-keyword">if</span> (_.isArray(obj)) <span class="hljs-keyword">return</span> slice.call(obj);
    <span class="hljs-keyword">if</span> (_.isString(obj)) {</pre></div></div>
            
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              <p>Keep surrogate pair characters together</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">return</span> obj.match(reStrSymbol);
    }
    <span class="hljs-keyword">if</span> (isArrayLike(obj)) <span class="hljs-keyword">return</span> _.map(obj, _.identity);
    <span class="hljs-keyword">return</span> _.values(obj);
  };</pre></div></div>
            
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              <p>Return the number of elements in an object.</p>

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            <div class="content"><div class='highlight'><pre>  _.size = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-number">0</span>;
    <span class="hljs-keyword">return</span> isArrayLike(obj) ? obj.length : _.keys(obj).length;
  };</pre></div></div>
            
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              <p>Split a collection into two arrays: one whose elements all satisfy the given
predicate, and one whose elements all do not satisfy the predicate.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.partition = group(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">result, value, pass</span>) </span>{
    result[pass ? <span class="hljs-number">0</span> : <span class="hljs-number">1</span>].push(value);
  }, <span class="hljs-literal">true</span>);</pre></div></div>
            
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              <h2 id="array-functions">Array Functions</h2>

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              <p>Get the first element of an array. Passing <strong>n</strong> will return the first N
values in the array. Aliased as <code>head</code> and <code>take</code>. The <strong>guard</strong> check
allows it to work with <code>_.map</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.first = _.head = _.take = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, n, guard</span>) </span>{
    <span class="hljs-keyword">if</span> (array == <span class="hljs-literal">null</span> || array.length &lt; <span class="hljs-number">1</span>) <span class="hljs-keyword">return</span> n == <span class="hljs-literal">null</span> ? <span class="hljs-keyword">void</span> <span class="hljs-number">0</span> : [];
    <span class="hljs-keyword">if</span> (n == <span class="hljs-literal">null</span> || guard) <span class="hljs-keyword">return</span> array[<span class="hljs-number">0</span>];
    <span class="hljs-keyword">return</span> _.initial(array, array.length - n);
  };</pre></div></div>
            
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              <p>Returns everything but the last entry of the array. Especially useful on
the arguments object. Passing <strong>n</strong> will return all the values in
the array, excluding the last N.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.initial = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, n, guard</span>) </span>{
    <span class="hljs-keyword">return</span> slice.call(array, <span class="hljs-number">0</span>, <span class="hljs-built_in">Math</span>.max(<span class="hljs-number">0</span>, array.length - (n == <span class="hljs-literal">null</span> || guard ? <span class="hljs-number">1</span> : n)));
  };</pre></div></div>
            
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              <p>Get the last element of an array. Passing <strong>n</strong> will return the last N
values in the array.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.last = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, n, guard</span>) </span>{
    <span class="hljs-keyword">if</span> (array == <span class="hljs-literal">null</span> || array.length &lt; <span class="hljs-number">1</span>) <span class="hljs-keyword">return</span> n == <span class="hljs-literal">null</span> ? <span class="hljs-keyword">void</span> <span class="hljs-number">0</span> : [];
    <span class="hljs-keyword">if</span> (n == <span class="hljs-literal">null</span> || guard) <span class="hljs-keyword">return</span> array[array.length - <span class="hljs-number">1</span>];
    <span class="hljs-keyword">return</span> _.rest(array, <span class="hljs-built_in">Math</span>.max(<span class="hljs-number">0</span>, array.length - n));
  };</pre></div></div>
            
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              <p>Returns everything but the first entry of the array. Aliased as <code>tail</code> and <code>drop</code>.
Especially useful on the arguments object. Passing an <strong>n</strong> will return
the rest N values in the array.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.rest = _.tail = _.drop = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, n, guard</span>) </span>{
    <span class="hljs-keyword">return</span> slice.call(array, n == <span class="hljs-literal">null</span> || guard ? <span class="hljs-number">1</span> : n);
  };</pre></div></div>
            
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              <p>Trim out all falsy values from an array.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.compact = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array</span>) </span>{
    <span class="hljs-keyword">return</span> _.filter(array, <span class="hljs-built_in">Boolean</span>);
  };</pre></div></div>
            
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              <p>Internal implementation of a recursive <code>flatten</code> function.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> flatten = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">input, shallow, strict, output</span>) </span>{
    output = output || [];
    <span class="hljs-keyword">var</span> idx = output.length;
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = getLength(input); i &lt; length; i++) {
      <span class="hljs-keyword">var</span> value = input[i];
      <span class="hljs-keyword">if</span> (isArrayLike(value) &amp;&amp; (_.isArray(value) || _.isArguments(value))) {</pre></div></div>
            
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              <p>Flatten current level of array or arguments object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>        <span class="hljs-keyword">if</span> (shallow) {
          <span class="hljs-keyword">var</span> j = <span class="hljs-number">0</span>, len = value.length;
          <span class="hljs-keyword">while</span> (j &lt; len) output[idx++] = value[j++];
        } <span class="hljs-keyword">else</span> {
          flatten(value, shallow, strict, output);
          idx = output.length;
        }
      } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (!strict) {
        output[idx++] = value;
      }
    }
    <span class="hljs-keyword">return</span> output;
  };</pre></div></div>
            
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              <p>Flatten out an array, either recursively (by default), or just one level.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.flatten = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, shallow</span>) </span>{
    <span class="hljs-keyword">return</span> flatten(array, shallow, <span class="hljs-literal">false</span>);
  };</pre></div></div>
            
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              <p>Return a version of the array that does not contain the specified value(s).</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.without = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, otherArrays</span>) </span>{
    <span class="hljs-keyword">return</span> _.difference(array, otherArrays);
  });</pre></div></div>
            
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              <p>Produce a duplicate-free version of the array. If the array has already
been sorted, you have the option of using a faster algorithm.
The faster algorithm will not work with an iteratee if the iteratee
is not a one-to-one function, so providing an iteratee will disable
the faster algorithm.
Aliased as <code>unique</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.uniq = _.unique = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, isSorted, iteratee, context</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isBoolean(isSorted)) {
      context = iteratee;
      iteratee = isSorted;
      isSorted = <span class="hljs-literal">false</span>;
    }
    <span class="hljs-keyword">if</span> (iteratee != <span class="hljs-literal">null</span>) iteratee = cb(iteratee, context);
    <span class="hljs-keyword">var</span> result = [];
    <span class="hljs-keyword">var</span> seen = [];
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = getLength(array); i &lt; length; i++) {
      <span class="hljs-keyword">var</span> value = array[i],
          computed = iteratee ? iteratee(value, i, array) : value;
      <span class="hljs-keyword">if</span> (isSorted &amp;&amp; !iteratee) {
        <span class="hljs-keyword">if</span> (!i || seen !== computed) result.push(value);
        seen = computed;
      } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (iteratee) {
        <span class="hljs-keyword">if</span> (!_.contains(seen, computed)) {
          seen.push(computed);
          result.push(value);
        }
      } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (!_.contains(result, value)) {
        result.push(value);
      }
    }
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              <p>Produce an array that contains the union: each distinct element from all of
the passed-in arrays.</p>

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            <div class="content"><div class='highlight'><pre>  _.union = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">arrays</span>) </span>{
    <span class="hljs-keyword">return</span> _.uniq(flatten(arrays, <span class="hljs-literal">true</span>, <span class="hljs-literal">true</span>));
  });</pre></div></div>
            
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              <p>Produce an array that contains every item shared between all the
passed-in arrays.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.intersection = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array</span>) </span>{
    <span class="hljs-keyword">var</span> result = [];
    <span class="hljs-keyword">var</span> argsLength = <span class="hljs-built_in">arguments</span>.length;
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = getLength(array); i &lt; length; i++) {
      <span class="hljs-keyword">var</span> item = array[i];
      <span class="hljs-keyword">if</span> (_.contains(result, item)) <span class="hljs-keyword">continue</span>;
      <span class="hljs-keyword">var</span> j;
      <span class="hljs-keyword">for</span> (j = <span class="hljs-number">1</span>; j &lt; argsLength; j++) {
        <span class="hljs-keyword">if</span> (!_.contains(<span class="hljs-built_in">arguments</span>[j], item)) <span class="hljs-keyword">break</span>;
      }
      <span class="hljs-keyword">if</span> (j === argsLength) result.push(item);
    }
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              <p>Take the difference between one array and a number of other arrays.
Only the elements present in just the first array will remain.</p>

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            <div class="content"><div class='highlight'><pre>  _.difference = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, rest</span>) </span>{
    rest = flatten(rest, <span class="hljs-literal">true</span>, <span class="hljs-literal">true</span>);
    <span class="hljs-keyword">return</span> _.filter(array, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value</span>)</span>{
      <span class="hljs-keyword">return</span> !_.contains(rest, value);
    });
  });</pre></div></div>
            
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              <p>Complement of _.zip. Unzip accepts an array of arrays and groups
each array’s elements on shared indices.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.unzip = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array</span>) </span>{
    <span class="hljs-keyword">var</span> length = array &amp;&amp; _.max(array, getLength).length || <span class="hljs-number">0</span>;
    <span class="hljs-keyword">var</span> result = <span class="hljs-built_in">Array</span>(length);

    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>; index &lt; length; index++) {
      result[index] = _.pluck(array, index);
    }
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              <p>Zip together multiple lists into a single array – elements that share
an index go together.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.zip = restArguments(_.unzip);</pre></div></div>
            
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              <p>Converts lists into objects. Pass either a single array of <code>[key, value]</code>
pairs, or two parallel arrays of the same length – one of keys, and one of
the corresponding values. Passing by pairs is the reverse of _.pairs.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.object = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">list, values</span>) </span>{
    <span class="hljs-keyword">var</span> result = {};
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = getLength(list); i &lt; length; i++) {
      <span class="hljs-keyword">if</span> (values) {
        result[list[i]] = values[i];
      } <span class="hljs-keyword">else</span> {
        result[list[i][<span class="hljs-number">0</span>]] = list[i][<span class="hljs-number">1</span>];
      }
    }
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              <p>Generator function to create the findIndex and findLastIndex functions.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> createPredicateIndexFinder = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">dir</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, predicate, context</span>) </span>{
      predicate = cb(predicate, context);
      <span class="hljs-keyword">var</span> length = getLength(array);
      <span class="hljs-keyword">var</span> index = dir &gt; <span class="hljs-number">0</span> ? <span class="hljs-number">0</span> : length - <span class="hljs-number">1</span>;
      <span class="hljs-keyword">for</span> (; index &gt;= <span class="hljs-number">0</span> &amp;&amp; index &lt; length; index += dir) {
        <span class="hljs-keyword">if</span> (predicate(array[index], index, array)) <span class="hljs-keyword">return</span> index;
      }
      <span class="hljs-keyword">return</span> <span class="hljs-number">-1</span>;
    };
  };</pre></div></div>
            
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              <p>Returns the first index on an array-like that passes a predicate test.</p>

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            <div class="content"><div class='highlight'><pre>  _.findIndex = createPredicateIndexFinder(<span class="hljs-number">1</span>);
  _.findLastIndex = createPredicateIndexFinder(<span class="hljs-number">-1</span>);</pre></div></div>
            
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              <p>Use a comparator function to figure out the smallest index at which
an object should be inserted so as to maintain order. Uses binary search.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.sortedIndex = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, obj, iteratee, context</span>) </span>{
    iteratee = cb(iteratee, context, <span class="hljs-number">1</span>);
    <span class="hljs-keyword">var</span> value = iteratee(obj);
    <span class="hljs-keyword">var</span> low = <span class="hljs-number">0</span>, high = getLength(array);
    <span class="hljs-keyword">while</span> (low &lt; high) {
      <span class="hljs-keyword">var</span> mid = <span class="hljs-built_in">Math</span>.floor((low + high) / <span class="hljs-number">2</span>);
      <span class="hljs-keyword">if</span> (iteratee(array[mid]) &lt; value) low = mid + <span class="hljs-number">1</span>; <span class="hljs-keyword">else</span> high = mid;
    }
    <span class="hljs-keyword">return</span> low;
  };</pre></div></div>
            
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              <p>Generator function to create the indexOf and lastIndexOf functions.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> createIndexFinder = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">dir, predicateFind, sortedIndex</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, item, idx</span>) </span>{
      <span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = getLength(array);
      <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> idx == <span class="hljs-string">'number'</span>) {
        <span class="hljs-keyword">if</span> (dir &gt; <span class="hljs-number">0</span>) {
          i = idx &gt;= <span class="hljs-number">0</span> ? idx : <span class="hljs-built_in">Math</span>.max(idx + length, i);
        } <span class="hljs-keyword">else</span> {
          length = idx &gt;= <span class="hljs-number">0</span> ? <span class="hljs-built_in">Math</span>.min(idx + <span class="hljs-number">1</span>, length) : idx + length + <span class="hljs-number">1</span>;
        }
      } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (sortedIndex &amp;&amp; idx &amp;&amp; length) {
        idx = sortedIndex(array, item);
        <span class="hljs-keyword">return</span> array[idx] === item ? idx : <span class="hljs-number">-1</span>;
      }
      <span class="hljs-keyword">if</span> (item !== item) {
        idx = predicateFind(slice.call(array, i, length), _.isNaN);
        <span class="hljs-keyword">return</span> idx &gt;= <span class="hljs-number">0</span> ? idx + i : <span class="hljs-number">-1</span>;
      }
      <span class="hljs-keyword">for</span> (idx = dir &gt; <span class="hljs-number">0</span> ? i : length - <span class="hljs-number">1</span>; idx &gt;= <span class="hljs-number">0</span> &amp;&amp; idx &lt; length; idx += dir) {
        <span class="hljs-keyword">if</span> (array[idx] === item) <span class="hljs-keyword">return</span> idx;
      }
      <span class="hljs-keyword">return</span> <span class="hljs-number">-1</span>;
    };
  };</pre></div></div>
            
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              <p>Return the position of the first occurrence of an item in an array,
or -1 if the item is not included in the array.
If the array is large and already in sort order, pass <code>true</code>
for <strong>isSorted</strong> to use binary search.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.indexOf = createIndexFinder(<span class="hljs-number">1</span>, _.findIndex, _.sortedIndex);
  _.lastIndexOf = createIndexFinder(<span class="hljs-number">-1</span>, _.findLastIndex);</pre></div></div>
            
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              <p>Generate an integer Array containing an arithmetic progression. A port of
the native Python <code>range()</code> function. See
<a href="https://docs.python.org/library/functions.html#range">the Python documentation</a>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.range = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">start, stop, step</span>) </span>{
    <span class="hljs-keyword">if</span> (stop == <span class="hljs-literal">null</span>) {
      stop = start || <span class="hljs-number">0</span>;
      start = <span class="hljs-number">0</span>;
    }
    <span class="hljs-keyword">if</span> (!step) {
      step = stop &lt; start ? <span class="hljs-number">-1</span> : <span class="hljs-number">1</span>;
    }

    <span class="hljs-keyword">var</span> length = <span class="hljs-built_in">Math</span>.max(<span class="hljs-built_in">Math</span>.ceil((stop - start) / step), <span class="hljs-number">0</span>);
    <span class="hljs-keyword">var</span> range = <span class="hljs-built_in">Array</span>(length);

    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> idx = <span class="hljs-number">0</span>; idx &lt; length; idx++, start += step) {
      range[idx] = start;
    }

    <span class="hljs-keyword">return</span> range;
  };</pre></div></div>
            
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              <p>Chunk a single array into multiple arrays, each containing <code>count</code> or fewer
items.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.chunk = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">array, count</span>) </span>{
    <span class="hljs-keyword">if</span> (count == <span class="hljs-literal">null</span> || count &lt; <span class="hljs-number">1</span>) <span class="hljs-keyword">return</span> [];
    <span class="hljs-keyword">var</span> result = [];
    <span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = array.length;
    <span class="hljs-keyword">while</span> (i &lt; length) {
      result.push(slice.call(array, i, i += count));
    }
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              </div>
              <h2 id="function-ahem-functions">Function (ahem) Functions</h2>

            </div>
            
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            </div>
            
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              <p>Determines whether to execute a function as a constructor
or a normal function with the provided arguments.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> executeBound = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">sourceFunc, boundFunc, context, callingContext, args</span>) </span>{
    <span class="hljs-keyword">if</span> (!(callingContext <span class="hljs-keyword">instanceof</span> boundFunc)) <span class="hljs-keyword">return</span> sourceFunc.apply(context, args);
    <span class="hljs-keyword">var</span> self = baseCreate(sourceFunc.prototype);
    <span class="hljs-keyword">var</span> result = sourceFunc.apply(self, args);
    <span class="hljs-keyword">if</span> (_.isObject(result)) <span class="hljs-keyword">return</span> result;
    <span class="hljs-keyword">return</span> self;
  };</pre></div></div>
            
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              <p>Create a function bound to a given object (assigning <code>this</code>, and arguments,
optionally). Delegates to <strong>ECMAScript 5</strong>‘s native <code>Function.bind</code> if
available.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.bind = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, context, args</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isFunction(func)) <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">TypeError</span>(<span class="hljs-string">'Bind must be called on a function'</span>);
    <span class="hljs-keyword">var</span> bound = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">callArgs</span>) </span>{
      <span class="hljs-keyword">return</span> executeBound(func, bound, context, <span class="hljs-keyword">this</span>, args.concat(callArgs));
    });
    <span class="hljs-keyword">return</span> bound;
  });</pre></div></div>
            
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              <p>Partially apply a function by creating a version that has had some of its
arguments pre-filled, without changing its dynamic <code>this</code> context. _ acts
as a placeholder by default, allowing any combination of arguments to be
pre-filled. Set <code>_.partial.placeholder</code> for a custom placeholder argument.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.partial = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, boundArgs</span>) </span>{
    <span class="hljs-keyword">var</span> placeholder = _.partial.placeholder;
    <span class="hljs-keyword">var</span> bound = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">var</span> position = <span class="hljs-number">0</span>, length = boundArgs.length;
      <span class="hljs-keyword">var</span> args = <span class="hljs-built_in">Array</span>(length);
      <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; length; i++) {
        args[i] = boundArgs[i] === placeholder ? <span class="hljs-built_in">arguments</span>[position++] : boundArgs[i];
      }
      <span class="hljs-keyword">while</span> (position &lt; <span class="hljs-built_in">arguments</span>.length) args.push(<span class="hljs-built_in">arguments</span>[position++]);
      <span class="hljs-keyword">return</span> executeBound(func, bound, <span class="hljs-keyword">this</span>, <span class="hljs-keyword">this</span>, args);
    };
    <span class="hljs-keyword">return</span> bound;
  });

  _.partial.placeholder = _;</pre></div></div>
            
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              <p>Bind a number of an object’s methods to that object. Remaining arguments
are the method names to be bound. Useful for ensuring that all callbacks
defined on an object belong to it.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.bindAll = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, keys</span>) </span>{
    keys = flatten(keys, <span class="hljs-literal">false</span>, <span class="hljs-literal">false</span>);
    <span class="hljs-keyword">var</span> index = keys.length;
    <span class="hljs-keyword">if</span> (index &lt; <span class="hljs-number">1</span>) <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Error</span>(<span class="hljs-string">'bindAll must be passed function names'</span>);
    <span class="hljs-keyword">while</span> (index--) {
      <span class="hljs-keyword">var</span> key = keys[index];
      obj[key] = _.bind(obj[key], obj);
    }
  });</pre></div></div>
            
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              <p>Memoize an expensive function by storing its results.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.memoize = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, hasher</span>) </span>{
    <span class="hljs-keyword">var</span> memoize = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">key</span>) </span>{
      <span class="hljs-keyword">var</span> cache = memoize.cache;
      <span class="hljs-keyword">var</span> address = <span class="hljs-string">''</span> + (hasher ? hasher.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>) : key);
      <span class="hljs-keyword">if</span> (!has(cache, address)) cache[address] = func.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>);
      <span class="hljs-keyword">return</span> cache[address];
    };
    memoize.cache = {};
    <span class="hljs-keyword">return</span> memoize;
  };</pre></div></div>
            
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              <p>Delays a function for the given number of milliseconds, and then calls
it with the arguments supplied.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.delay = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, wait, args</span>) </span>{
    <span class="hljs-keyword">return</span> setTimeout(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">return</span> func.apply(<span class="hljs-literal">null</span>, args);
    }, wait);
  });</pre></div></div>
            
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              </div>
              <p>Defers a function, scheduling it to run after the current call stack has
cleared.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.defer = _.partial(_.delay, _, <span class="hljs-number">1</span>);</pre></div></div>
            
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              </div>
              <p>Returns a function, that, when invoked, will only be triggered at most once
during a given window of time. Normally, the throttled function will run
as much as it can, without ever going more than once per <code>wait</code> duration;
but if you’d like to disable the execution on the leading edge, pass
<code>{leading: false}</code>. To disable execution on the trailing edge, ditto.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.throttle = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, wait, options</span>) </span>{
    <span class="hljs-keyword">var</span> timeout, context, args, result;
    <span class="hljs-keyword">var</span> previous = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">if</span> (!options) options = {};

    <span class="hljs-keyword">var</span> later = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      previous = options.leading === <span class="hljs-literal">false</span> ? <span class="hljs-number">0</span> : _.now();
      timeout = <span class="hljs-literal">null</span>;
      result = func.apply(context, args);
      <span class="hljs-keyword">if</span> (!timeout) context = args = <span class="hljs-literal">null</span>;
    };

    <span class="hljs-keyword">var</span> throttled = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">var</span> now = _.now();
      <span class="hljs-keyword">if</span> (!previous &amp;&amp; options.leading === <span class="hljs-literal">false</span>) previous = now;
      <span class="hljs-keyword">var</span> remaining = wait - (now - previous);
      context = <span class="hljs-keyword">this</span>;
      args = <span class="hljs-built_in">arguments</span>;
      <span class="hljs-keyword">if</span> (remaining &lt;= <span class="hljs-number">0</span> || remaining &gt; wait) {
        <span class="hljs-keyword">if</span> (timeout) {
          clearTimeout(timeout);
          timeout = <span class="hljs-literal">null</span>;
        }
        previous = now;
        result = func.apply(context, args);
        <span class="hljs-keyword">if</span> (!timeout) context = args = <span class="hljs-literal">null</span>;
      } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (!timeout &amp;&amp; options.trailing !== <span class="hljs-literal">false</span>) {
        timeout = setTimeout(later, remaining);
      }
      <span class="hljs-keyword">return</span> result;
    };

    throttled.cancel = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      clearTimeout(timeout);
      previous = <span class="hljs-number">0</span>;
      timeout = context = args = <span class="hljs-literal">null</span>;
    };

    <span class="hljs-keyword">return</span> throttled;
  };</pre></div></div>
            
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              <p>Returns a function, that, as long as it continues to be invoked, will not
be triggered. The function will be called after it stops being called for
N milliseconds. If <code>immediate</code> is passed, trigger the function on the
leading edge, instead of the trailing.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.debounce = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, wait, immediate</span>) </span>{
    <span class="hljs-keyword">var</span> timeout, result;

    <span class="hljs-keyword">var</span> later = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">context, args</span>) </span>{
      timeout = <span class="hljs-literal">null</span>;
      <span class="hljs-keyword">if</span> (args) result = func.apply(context, args);
    };

    <span class="hljs-keyword">var</span> debounced = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">args</span>) </span>{
      <span class="hljs-keyword">if</span> (timeout) clearTimeout(timeout);
      <span class="hljs-keyword">if</span> (immediate) {
        <span class="hljs-keyword">var</span> callNow = !timeout;
        timeout = setTimeout(later, wait);
        <span class="hljs-keyword">if</span> (callNow) result = func.apply(<span class="hljs-keyword">this</span>, args);
      } <span class="hljs-keyword">else</span> {
        timeout = _.delay(later, wait, <span class="hljs-keyword">this</span>, args);
      }

      <span class="hljs-keyword">return</span> result;
    });

    debounced.cancel = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      clearTimeout(timeout);
      timeout = <span class="hljs-literal">null</span>;
    };

    <span class="hljs-keyword">return</span> debounced;
  };</pre></div></div>
            
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              <p>Returns the first function passed as an argument to the second,
allowing you to adjust arguments, run code before and after, and
conditionally execute the original function.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.wrap = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">func, wrapper</span>) </span>{
    <span class="hljs-keyword">return</span> _.partial(wrapper, func);
  };</pre></div></div>
            
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              <p>Returns a negated version of the passed-in predicate.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.negate = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">predicate</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">return</span> !predicate.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>);
    };
  };</pre></div></div>
            
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              </div>
              <p>Returns a function that is the composition of a list of functions, each
consuming the return value of the function that follows.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.compose = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
    <span class="hljs-keyword">var</span> args = <span class="hljs-built_in">arguments</span>;
    <span class="hljs-keyword">var</span> start = args.length - <span class="hljs-number">1</span>;
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">var</span> i = start;
      <span class="hljs-keyword">var</span> result = args[start].apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>);
      <span class="hljs-keyword">while</span> (i--) result = args[i].call(<span class="hljs-keyword">this</span>, result);
      <span class="hljs-keyword">return</span> result;
    };
  };</pre></div></div>
            
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              <p>Returns a function that will only be executed on and after the Nth call.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.after = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">times, func</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">if</span> (--times &lt; <span class="hljs-number">1</span>) {
        <span class="hljs-keyword">return</span> func.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>);
      }
    };
  };</pre></div></div>
            
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              <p>Returns a function that will only be executed up to (but not including) the Nth call.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.before = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">times, func</span>) </span>{
    <span class="hljs-keyword">var</span> memo;
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">if</span> (--times &gt; <span class="hljs-number">0</span>) {
        memo = func.apply(<span class="hljs-keyword">this</span>, <span class="hljs-built_in">arguments</span>);
      }
      <span class="hljs-keyword">if</span> (times &lt;= <span class="hljs-number">1</span>) func = <span class="hljs-literal">null</span>;
      <span class="hljs-keyword">return</span> memo;
    };
  };</pre></div></div>
            
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              <p>Returns a function that will be executed at most one time, no matter how
often you call it. Useful for lazy initialization.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.once = _.partial(_.before, <span class="hljs-number">2</span>);

  _.restArguments = restArguments;</pre></div></div>
            
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              <h2 id="object-functions">Object Functions</h2>

            </div>
            
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            </div>
            
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              <p>Keys in IE &lt; 9 that won’t be iterated by <code>for key in ...</code> and thus missed.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> hasEnumBug = !{<span class="hljs-attr">toString</span>: <span class="hljs-literal">null</span>}.propertyIsEnumerable(<span class="hljs-string">'toString'</span>);
  <span class="hljs-keyword">var</span> nonEnumerableProps = [<span class="hljs-string">'valueOf'</span>, <span class="hljs-string">'isPrototypeOf'</span>, <span class="hljs-string">'toString'</span>,
    <span class="hljs-string">'propertyIsEnumerable'</span>, <span class="hljs-string">'hasOwnProperty'</span>, <span class="hljs-string">'toLocaleString'</span>];

  <span class="hljs-keyword">var</span> collectNonEnumProps = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, keys</span>) </span>{
    <span class="hljs-keyword">var</span> nonEnumIdx = nonEnumerableProps.length;
    <span class="hljs-keyword">var</span> <span class="hljs-keyword">constructor</span> = obj.<span class="hljs-keyword">constructor</span>;
    var proto = _.isFunction(<span class="hljs-keyword">constructor</span>) &amp;&amp; <span class="hljs-keyword">constructor</span>.prototype || ObjProto;</pre></div></div>
            
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              <p>Constructor is a special case.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">var</span> prop = <span class="hljs-string">'constructor'</span>;
    <span class="hljs-keyword">if</span> (has(obj, prop) &amp;&amp; !_.contains(keys, prop)) keys.push(prop);

    <span class="hljs-keyword">while</span> (nonEnumIdx--) {
      prop = nonEnumerableProps[nonEnumIdx];
      <span class="hljs-keyword">if</span> (prop <span class="hljs-keyword">in</span> obj &amp;&amp; obj[prop] !== proto[prop] &amp;&amp; !_.contains(keys, prop)) {
        keys.push(prop);
      }
    }
  };</pre></div></div>
            
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              <p>Retrieve the names of an object’s own properties.
Delegates to <strong>ECMAScript 5</strong>‘s native <code>Object.keys</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.keys = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isObject(obj)) <span class="hljs-keyword">return</span> [];
    <span class="hljs-keyword">if</span> (nativeKeys) <span class="hljs-keyword">return</span> nativeKeys(obj);
    <span class="hljs-keyword">var</span> keys = [];
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> obj) <span class="hljs-keyword">if</span> (has(obj, key)) keys.push(key);</pre></div></div>
            
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              <p>Ahem, IE &lt; 9.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">if</span> (hasEnumBug) collectNonEnumProps(obj, keys);
    <span class="hljs-keyword">return</span> keys;
  };</pre></div></div>
            
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              <p>Retrieve all the property names of an object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.allKeys = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isObject(obj)) <span class="hljs-keyword">return</span> [];
    <span class="hljs-keyword">var</span> keys = [];
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> obj) keys.push(key);</pre></div></div>
            
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              <p>Ahem, IE &lt; 9.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">if</span> (hasEnumBug) collectNonEnumProps(obj, keys);
    <span class="hljs-keyword">return</span> keys;
  };</pre></div></div>
            
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              <p>Retrieve the values of an object’s properties.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.values = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">var</span> keys = _.keys(obj);
    <span class="hljs-keyword">var</span> length = keys.length;
    <span class="hljs-keyword">var</span> values = <span class="hljs-built_in">Array</span>(length);
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; length; i++) {
      values[i] = obj[keys[i]];
    }
    <span class="hljs-keyword">return</span> values;
  };</pre></div></div>
            
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              <p>Returns the results of applying the iteratee to each element of the object.
In contrast to _.map it returns an object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.mapObject = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, iteratee, context</span>) </span>{
    iteratee = cb(iteratee, context);
    <span class="hljs-keyword">var</span> keys = _.keys(obj),
        length = keys.length,
        results = {};
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>; index &lt; length; index++) {
      <span class="hljs-keyword">var</span> currentKey = keys[index];
      results[currentKey] = iteratee(obj[currentKey], currentKey, obj);
    }
    <span class="hljs-keyword">return</span> results;
  };</pre></div></div>
            
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              <p>Convert an object into a list of <code>[key, value]</code> pairs.
The opposite of _.object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.pairs = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">var</span> keys = _.keys(obj);
    <span class="hljs-keyword">var</span> length = keys.length;
    <span class="hljs-keyword">var</span> pairs = <span class="hljs-built_in">Array</span>(length);
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; length; i++) {
      pairs[i] = [keys[i], obj[keys[i]]];
    }
    <span class="hljs-keyword">return</span> pairs;
  };</pre></div></div>
            
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              <p>Invert the keys and values of an object. The values must be serializable.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.invert = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">var</span> result = {};
    <span class="hljs-keyword">var</span> keys = _.keys(obj);
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = keys.length; i &lt; length; i++) {
      result[obj[keys[i]]] = keys[i];
    }
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              <p>Return a sorted list of the function names available on the object.
Aliased as <code>methods</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.functions = _.methods = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">var</span> names = [];
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> obj) {
      <span class="hljs-keyword">if</span> (_.isFunction(obj[key])) names.push(key);
    }
    <span class="hljs-keyword">return</span> names.sort();
  };</pre></div></div>
            
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              <p>An internal function for creating assigner functions.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> createAssigner = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">keysFunc, defaults</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
      <span class="hljs-keyword">var</span> length = <span class="hljs-built_in">arguments</span>.length;
      <span class="hljs-keyword">if</span> (defaults) obj = <span class="hljs-built_in">Object</span>(obj);
      <span class="hljs-keyword">if</span> (length &lt; <span class="hljs-number">2</span> || obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> obj;
      <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> index = <span class="hljs-number">1</span>; index &lt; length; index++) {
        <span class="hljs-keyword">var</span> source = <span class="hljs-built_in">arguments</span>[index],
            keys = keysFunc(source),
            l = keys.length;
        <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; l; i++) {
          <span class="hljs-keyword">var</span> key = keys[i];
          <span class="hljs-keyword">if</span> (!defaults || obj[key] === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>) obj[key] = source[key];
        }
      }
      <span class="hljs-keyword">return</span> obj;
    };
  };</pre></div></div>
            
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              <p>Extend a given object with all the properties in passed-in object(s).</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.extend = createAssigner(_.allKeys);</pre></div></div>
            
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              <p>Assigns a given object with all the own properties in the passed-in object(s).
(<a href="https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/assign">https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object/assign</a>)</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.extendOwn = _.assign = createAssigner(_.keys);</pre></div></div>
            
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              <p>Returns the first key on an object that passes a predicate test.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.findKey = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, predicate, context</span>) </span>{
    predicate = cb(predicate, context);
    <span class="hljs-keyword">var</span> keys = _.keys(obj), key;
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = keys.length; i &lt; length; i++) {
      key = keys[i];
      <span class="hljs-keyword">if</span> (predicate(obj[key], key, obj)) <span class="hljs-keyword">return</span> key;
    }
  };</pre></div></div>
            
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              <p>Internal pick helper function to determine if <code>obj</code> has key <code>key</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> keyInObj = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value, key, obj</span>) </span>{
    <span class="hljs-keyword">return</span> key <span class="hljs-keyword">in</span> obj;
  };</pre></div></div>
            
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              <p>Return a copy of the object only containing the whitelisted properties.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.pick = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, keys</span>) </span>{
    <span class="hljs-keyword">var</span> result = {}, iteratee = keys[<span class="hljs-number">0</span>];
    <span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> result;
    <span class="hljs-keyword">if</span> (_.isFunction(iteratee)) {
      <span class="hljs-keyword">if</span> (keys.length &gt; <span class="hljs-number">1</span>) iteratee = optimizeCb(iteratee, keys[<span class="hljs-number">1</span>]);
      keys = _.allKeys(obj);
    } <span class="hljs-keyword">else</span> {
      iteratee = keyInObj;
      keys = flatten(keys, <span class="hljs-literal">false</span>, <span class="hljs-literal">false</span>);
      obj = <span class="hljs-built_in">Object</span>(obj);
    }
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>, length = keys.length; i &lt; length; i++) {
      <span class="hljs-keyword">var</span> key = keys[i];
      <span class="hljs-keyword">var</span> value = obj[key];
      <span class="hljs-keyword">if</span> (iteratee(value, key, obj)) result[key] = value;
    }
    <span class="hljs-keyword">return</span> result;
  });</pre></div></div>
            
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              <p>Return a copy of the object without the blacklisted properties.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.omit = restArguments(<span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, keys</span>) </span>{
    <span class="hljs-keyword">var</span> iteratee = keys[<span class="hljs-number">0</span>], context;
    <span class="hljs-keyword">if</span> (_.isFunction(iteratee)) {
      iteratee = _.negate(iteratee);
      <span class="hljs-keyword">if</span> (keys.length &gt; <span class="hljs-number">1</span>) context = keys[<span class="hljs-number">1</span>];
    } <span class="hljs-keyword">else</span> {
      keys = _.map(flatten(keys, <span class="hljs-literal">false</span>, <span class="hljs-literal">false</span>), <span class="hljs-built_in">String</span>);
      iteratee = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value, key</span>) </span>{
        <span class="hljs-keyword">return</span> !_.contains(keys, key);
      };
    }
    <span class="hljs-keyword">return</span> _.pick(obj, iteratee, context);
  });</pre></div></div>
            
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              <p>Fill in a given object with default properties.</p>

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            <div class="content"><div class='highlight'><pre>  _.defaults = createAssigner(_.allKeys, <span class="hljs-literal">true</span>);</pre></div></div>
            
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              <p>Creates an object that inherits from the given prototype object.
If additional properties are provided then they will be added to the
created object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.create = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">prototype, props</span>) </span>{
    <span class="hljs-keyword">var</span> result = baseCreate(prototype);
    <span class="hljs-keyword">if</span> (props) _.extendOwn(result, props);
    <span class="hljs-keyword">return</span> result;
  };</pre></div></div>
            
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              <p>Create a (shallow-cloned) duplicate of an object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.clone = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isObject(obj)) <span class="hljs-keyword">return</span> obj;
    <span class="hljs-keyword">return</span> _.isArray(obj) ? obj.slice() : _.extend({}, obj);
  };</pre></div></div>
            
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              <p>Invokes interceptor with the obj, and then returns obj.
The primary purpose of this method is to “tap into” a method chain, in
order to perform operations on intermediate results within the chain.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.tap = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, interceptor</span>) </span>{
    interceptor(obj);
    <span class="hljs-keyword">return</span> obj;
  };</pre></div></div>
            
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              <p>Returns whether an object has a given set of <code>key:value</code> pairs.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isMatch = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">object, attrs</span>) </span>{
    <span class="hljs-keyword">var</span> keys = _.keys(attrs), length = keys.length;
    <span class="hljs-keyword">if</span> (object == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> !length;
    <span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>(object);
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; length; i++) {
      <span class="hljs-keyword">var</span> key = keys[i];
      <span class="hljs-keyword">if</span> (attrs[key] !== obj[key] || !(key <span class="hljs-keyword">in</span> obj)) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
    }
    <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
  };</pre></div></div>
            
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              <p>Internal recursive comparison function for <code>isEqual</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> eq, deepEq;
  eq = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">a, b, aStack, bStack</span>) </span>{</pre></div></div>
            
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              <p>Identical objects are equal. <code>0 === -0</code>, but they aren’t identical.
See the <a href="https://wiki.ecmascript.org/doku.php?id=harmony:egal">Harmony <code>egal</code> proposal</a>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">if</span> (a === b) <span class="hljs-keyword">return</span> a !== <span class="hljs-number">0</span> || <span class="hljs-number">1</span> / a === <span class="hljs-number">1</span> / b;</pre></div></div>
            
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              <p><code>null</code> or <code>undefined</code> only equal to itself (strict comparison).</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">if</span> (a == <span class="hljs-literal">null</span> || b == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;</pre></div></div>
            
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              <p><code>NaN</code>s are equivalent, but non-reflexive.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">if</span> (a !== a) <span class="hljs-keyword">return</span> b !== b;</pre></div></div>
            
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              <p>Exhaust primitive checks</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">var</span> type = <span class="hljs-keyword">typeof</span> a;
    <span class="hljs-keyword">if</span> (type !== <span class="hljs-string">'function'</span> &amp;&amp; type !== <span class="hljs-string">'object'</span> &amp;&amp; <span class="hljs-keyword">typeof</span> b != <span class="hljs-string">'object'</span>) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
    <span class="hljs-keyword">return</span> deepEq(a, b, aStack, bStack);
  };</pre></div></div>
            
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              <p>Internal recursive comparison function for <code>isEqual</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  deepEq = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">a, b, aStack, bStack</span>) </span>{</pre></div></div>
            
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              <p>Unwrap any wrapped objects.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">if</span> (a <span class="hljs-keyword">instanceof</span> _) a = a._wrapped;
    <span class="hljs-keyword">if</span> (b <span class="hljs-keyword">instanceof</span> _) b = b._wrapped;</pre></div></div>
            
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              <p>Compare <code>[[Class]]</code> names.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">var</span> className = toString.call(a);
    <span class="hljs-keyword">if</span> (className !== toString.call(b)) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
    <span class="hljs-keyword">switch</span> (className) {</pre></div></div>
            
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              <p>Strings, numbers, regular expressions, dates, and booleans are compared by value.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">case</span> <span class="hljs-string">'[object RegExp]'</span>:</pre></div></div>
            
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              <p>RegExps are coerced to strings for comparison (Note: ‘’ + /a/i === ‘/a/i’)</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">case</span> <span class="hljs-string">'[object String]'</span>:</pre></div></div>
            
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              <p>Primitives and their corresponding object wrappers are equivalent; thus, <code>&quot;5&quot;</code> is
equivalent to <code>new String(&quot;5&quot;)</code>.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>        <span class="hljs-keyword">return</span> <span class="hljs-string">''</span> + a === <span class="hljs-string">''</span> + b;
      <span class="hljs-keyword">case</span> <span class="hljs-string">'[object Number]'</span>:</pre></div></div>
            
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              <p><code>NaN</code>s are equivalent, but non-reflexive.
Object(NaN) is equivalent to NaN.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>        <span class="hljs-keyword">if</span> (+a !== +a) <span class="hljs-keyword">return</span> +b !== +b;</pre></div></div>
            
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              <p>An <code>egal</code> comparison is performed for other numeric values.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>        <span class="hljs-keyword">return</span> +a === <span class="hljs-number">0</span> ? <span class="hljs-number">1</span> / +a === <span class="hljs-number">1</span> / b : +a === +b;
      <span class="hljs-keyword">case</span> <span class="hljs-string">'[object Date]'</span>:
      <span class="hljs-keyword">case</span> <span class="hljs-string">'[object Boolean]'</span>:</pre></div></div>
            
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              <p>Coerce dates and booleans to numeric primitive values. Dates are compared by their
millisecond representations. Note that invalid dates with millisecond representations
of <code>NaN</code> are not equivalent.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>        <span class="hljs-keyword">return</span> +a === +b;
      <span class="hljs-keyword">case</span> <span class="hljs-string">'[object Symbol]'</span>:
        <span class="hljs-keyword">return</span> SymbolProto.valueOf.call(a) === SymbolProto.valueOf.call(b);
    }

    <span class="hljs-keyword">var</span> areArrays = className === <span class="hljs-string">'[object Array]'</span>;
    <span class="hljs-keyword">if</span> (!areArrays) {
      <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> a != <span class="hljs-string">'object'</span> || <span class="hljs-keyword">typeof</span> b != <span class="hljs-string">'object'</span>) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;</pre></div></div>
            
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              <p>Objects with different constructors are not equivalent, but <code>Object</code>s or <code>Array</code>s
from different frames are.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">var</span> aCtor = a.constructor, bCtor = b.constructor;
      <span class="hljs-keyword">if</span> (aCtor !== bCtor &amp;&amp; !(_.isFunction(aCtor) &amp;&amp; aCtor <span class="hljs-keyword">instanceof</span> aCtor &amp;&amp;
                               _.isFunction(bCtor) &amp;&amp; bCtor <span class="hljs-keyword">instanceof</span> bCtor)
                          &amp;&amp; (<span class="hljs-string">'constructor'</span> <span class="hljs-keyword">in</span> a &amp;&amp; <span class="hljs-string">'constructor'</span> <span class="hljs-keyword">in</span> b)) {
        <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
      }
    }</pre></div></div>
            
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              <p>Assume equality for cyclic structures. The algorithm for detecting cyclic
structures is adapted from ES 5.1 section 15.12.3, abstract operation <code>JO</code>.</p>

            </div>
            
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              <p>Initializing stack of traversed objects.
It’s done here since we only need them for objects and arrays comparison.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    aStack = aStack || [];
    bStack = bStack || [];
    <span class="hljs-keyword">var</span> length = aStack.length;
    <span class="hljs-keyword">while</span> (length--) {</pre></div></div>
            
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              <p>Linear search. Performance is inversely proportional to the number of
unique nested structures.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">if</span> (aStack[length] === a) <span class="hljs-keyword">return</span> bStack[length] === b;
    }</pre></div></div>
            
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              <p>Add the first object to the stack of traversed objects.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    aStack.push(a);
    bStack.push(b);</pre></div></div>
            
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              <p>Recursively compare objects and arrays.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">if</span> (areArrays) {</pre></div></div>
            
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              <p>Compare array lengths to determine if a deep comparison is necessary.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      length = a.length;
      <span class="hljs-keyword">if</span> (length !== b.length) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;</pre></div></div>
            
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        <li id="section-139">
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              <p>Deep compare the contents, ignoring non-numeric properties.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">while</span> (length--) {
        <span class="hljs-keyword">if</span> (!eq(a[length], b[length], aStack, bStack)) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
      }
    } <span class="hljs-keyword">else</span> {</pre></div></div>
            
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        <li id="section-140">
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              <p>Deep compare objects.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">var</span> keys = _.keys(a), key;
      length = keys.length;</pre></div></div>
            
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              <p>Ensure that both objects contain the same number of properties before comparing deep equality.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">if</span> (_.keys(b).length !== length) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
      <span class="hljs-keyword">while</span> (length--) {</pre></div></div>
            
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              <p>Deep compare each member</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>        key = keys[length];
        <span class="hljs-keyword">if</span> (!(has(b, key) &amp;&amp; eq(a[key], b[key], aStack, bStack))) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
      }
    }</pre></div></div>
            
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              <p>Remove the first object from the stack of traversed objects.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    aStack.pop();
    bStack.pop();
    <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
  };</pre></div></div>
            
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        <li id="section-144">
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              <p>Perform a deep comparison to check if two objects are equal.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isEqual = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">a, b</span>) </span>{
    <span class="hljs-keyword">return</span> eq(a, b);
  };</pre></div></div>
            
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              <p>Is a given array, string, or object empty?
An “empty” object has no enumerable own-properties.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isEmpty = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
    <span class="hljs-keyword">if</span> (isArrayLike(obj) &amp;&amp; (_.isArray(obj) || _.isString(obj) || _.isArguments(obj))) <span class="hljs-keyword">return</span> obj.length === <span class="hljs-number">0</span>;
    <span class="hljs-keyword">return</span> _.keys(obj).length === <span class="hljs-number">0</span>;
  };</pre></div></div>
            
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              <p>Is a given value a DOM element?</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isElement = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">return</span> !!(obj &amp;&amp; obj.nodeType === <span class="hljs-number">1</span>);
  };</pre></div></div>
            
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              <p>Is a given value an array?
Delegates to ECMA5’s native Array.isArray</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isArray = nativeIsArray || <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">return</span> toString.call(obj) === <span class="hljs-string">'[object Array]'</span>;
  };</pre></div></div>
            
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              <p>Is a given variable an object?</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isObject = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">var</span> type = <span class="hljs-keyword">typeof</span> obj;
    <span class="hljs-keyword">return</span> type === <span class="hljs-string">'function'</span> || type === <span class="hljs-string">'object'</span> &amp;&amp; !!obj;
  };</pre></div></div>
            
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              <p>Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp, isError, isMap, isWeakMap, isSet, isWeakSet.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.each([<span class="hljs-string">'Arguments'</span>, <span class="hljs-string">'Function'</span>, <span class="hljs-string">'String'</span>, <span class="hljs-string">'Number'</span>, <span class="hljs-string">'Date'</span>, <span class="hljs-string">'RegExp'</span>, <span class="hljs-string">'Error'</span>, <span class="hljs-string">'Symbol'</span>, <span class="hljs-string">'Map'</span>, <span class="hljs-string">'WeakMap'</span>, <span class="hljs-string">'Set'</span>, <span class="hljs-string">'WeakSet'</span>], <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">name</span>) </span>{
    _[<span class="hljs-string">'is'</span> + name] = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
      <span class="hljs-keyword">return</span> toString.call(obj) === <span class="hljs-string">'[object '</span> + name + <span class="hljs-string">']'</span>;
    };
  });</pre></div></div>
            
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              <p>Define a fallback version of the method in browsers (ahem, IE &lt; 9), where
there isn’t any inspectable “Arguments” type.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">if</span> (!_.isArguments(<span class="hljs-built_in">arguments</span>)) {
    _.isArguments = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
      <span class="hljs-keyword">return</span> has(obj, <span class="hljs-string">'callee'</span>);
    };
  }</pre></div></div>
            
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              <p>Optimize <code>isFunction</code> if appropriate. Work around some typeof bugs in old v8,
IE 11 (#1621), Safari 8 (#1929), and PhantomJS (#2236).</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> nodelist = root.document &amp;&amp; root.document.childNodes;
  <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> /./ != <span class="hljs-string">'function'</span> &amp;&amp; <span class="hljs-keyword">typeof</span> <span class="hljs-built_in">Int8Array</span> != <span class="hljs-string">'object'</span> &amp;&amp; <span class="hljs-keyword">typeof</span> nodelist != <span class="hljs-string">'function'</span>) {
    _.isFunction = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
      <span class="hljs-keyword">return</span> <span class="hljs-keyword">typeof</span> obj == <span class="hljs-string">'function'</span> || <span class="hljs-literal">false</span>;
    };
  }</pre></div></div>
            
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              <p>Is a given object a finite number?</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isFinite = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">return</span> !_.isSymbol(obj) &amp;&amp; <span class="hljs-built_in">isFinite</span>(obj) &amp;&amp; !<span class="hljs-built_in">isNaN</span>(<span class="hljs-built_in">parseFloat</span>(obj));
  };</pre></div></div>
            
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              <p>Is the given value <code>NaN</code>?</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isNaN = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">return</span> _.isNumber(obj) &amp;&amp; <span class="hljs-built_in">isNaN</span>(obj);
  };</pre></div></div>
            
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              <p>Is a given value a boolean?</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isBoolean = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">return</span> obj === <span class="hljs-literal">true</span> || obj === <span class="hljs-literal">false</span> || toString.call(obj) === <span class="hljs-string">'[object Boolean]'</span>;
  };</pre></div></div>
            
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              <p>Is a given value equal to null?</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isNull = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">return</span> obj === <span class="hljs-literal">null</span>;
  };</pre></div></div>
            
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              <p>Is a given variable undefined?</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.isUndefined = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">return</span> obj === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>;
  };</pre></div></div>
            
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              <p>Shortcut function for checking if an object has a given property directly
on itself (in other words, not on a prototype).</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.has = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, path</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isArray(path)) {
      <span class="hljs-keyword">return</span> has(obj, path);
    }
    <span class="hljs-keyword">var</span> length = path.length;
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; length; i++) {
      <span class="hljs-keyword">var</span> key = path[i];
      <span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span> || !hasOwnProperty.call(obj, key)) {
        <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
      }
      obj = obj[key];
    }
    <span class="hljs-keyword">return</span> !!length;
  };</pre></div></div>
            
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              <h2 id="utility-functions">Utility Functions</h2>

            </div>
            
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            </div>
            
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              <p>Run Underscore.js in <em>noConflict</em> mode, returning the <code>_</code> variable to its
previous owner. Returns a reference to the Underscore object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.noConflict = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
    root._ = previousUnderscore;
    <span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>;
  };</pre></div></div>
            
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              <p>Keep the identity function around for default iteratees.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.identity = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value</span>) </span>{
    <span class="hljs-keyword">return</span> value;
  };</pre></div></div>
            
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              <p>Predicate-generating functions. Often useful outside of Underscore.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.constant = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">value</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">return</span> value;
    };
  };

  _.noop = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>)</span>{};</pre></div></div>
            
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              <p>Creates a function that, when passed an object, will traverse that object’s
properties down the given <code>path</code>, specified as an array of keys or indexes.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.property = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">path</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isArray(path)) {
      <span class="hljs-keyword">return</span> shallowProperty(path);
    }
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
      <span class="hljs-keyword">return</span> deepGet(obj, path);
    };
  };</pre></div></div>
            
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              <p>Generates a function for a given object that returns a given property.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.propertyOf = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">if</span> (obj == <span class="hljs-literal">null</span>) {
      <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>)</span>{};
    }
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">path</span>) </span>{
      <span class="hljs-keyword">return</span> !_.isArray(path) ? obj[path] : deepGet(obj, path);
    };
  };</pre></div></div>
            
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              <p>Returns a predicate for checking whether an object has a given set of
<code>key:value</code> pairs.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.matcher = _.matches = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">attrs</span>) </span>{
    attrs = _.extendOwn({}, attrs);
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
      <span class="hljs-keyword">return</span> _.isMatch(obj, attrs);
    };
  };</pre></div></div>
            
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              <p>Run a function <strong>n</strong> times.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.times = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">n, iteratee, context</span>) </span>{
    <span class="hljs-keyword">var</span> accum = <span class="hljs-built_in">Array</span>(<span class="hljs-built_in">Math</span>.max(<span class="hljs-number">0</span>, n));
    iteratee = optimizeCb(iteratee, context, <span class="hljs-number">1</span>);
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; n; i++) accum[i] = iteratee(i);
    <span class="hljs-keyword">return</span> accum;
  };</pre></div></div>
            
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              <p>Return a random integer between min and max (inclusive).</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.random = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">min, max</span>) </span>{
    <span class="hljs-keyword">if</span> (max == <span class="hljs-literal">null</span>) {
      max = min;
      min = <span class="hljs-number">0</span>;
    }
    <span class="hljs-keyword">return</span> min + <span class="hljs-built_in">Math</span>.floor(<span class="hljs-built_in">Math</span>.random() * (max - min + <span class="hljs-number">1</span>));
  };</pre></div></div>
            
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              <p>A (possibly faster) way to get the current timestamp as an integer.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.now = <span class="hljs-built_in">Date</span>.now || <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Date</span>().getTime();
  };</pre></div></div>
            
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              <p>List of HTML entities for escaping.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> escapeMap = {
    <span class="hljs-string">'&amp;'</span>: <span class="hljs-string">'&amp;amp;'</span>,
    <span class="hljs-string">'&lt;'</span>: <span class="hljs-string">'&amp;lt;'</span>,
    <span class="hljs-string">'&gt;'</span>: <span class="hljs-string">'&amp;gt;'</span>,
    <span class="hljs-string">'"'</span>: <span class="hljs-string">'&amp;quot;'</span>,
    <span class="hljs-string">"'"</span>: <span class="hljs-string">'&amp;#x27;'</span>,
    <span class="hljs-string">'`'</span>: <span class="hljs-string">'&amp;#x60;'</span>
  };
  <span class="hljs-keyword">var</span> unescapeMap = _.invert(escapeMap);</pre></div></div>
            
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              <p>Functions for escaping and unescaping strings to/from HTML interpolation.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> createEscaper = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">map</span>) </span>{
    <span class="hljs-keyword">var</span> escaper = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">match</span>) </span>{
      <span class="hljs-keyword">return</span> map[match];
    };</pre></div></div>
            
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              <p>Regexes for identifying a key that needs to be escaped.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">var</span> source = <span class="hljs-string">'(?:'</span> + _.keys(map).join(<span class="hljs-string">'|'</span>) + <span class="hljs-string">')'</span>;
    <span class="hljs-keyword">var</span> testRegexp = <span class="hljs-built_in">RegExp</span>(source);
    <span class="hljs-keyword">var</span> replaceRegexp = <span class="hljs-built_in">RegExp</span>(source, <span class="hljs-string">'g'</span>);
    <span class="hljs-keyword">return</span> <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">string</span>) </span>{
      string = string == <span class="hljs-literal">null</span> ? <span class="hljs-string">''</span> : <span class="hljs-string">''</span> + string;
      <span class="hljs-keyword">return</span> testRegexp.test(string) ? string.replace(replaceRegexp, escaper) : string;
    };
  };
  _.escape = createEscaper(escapeMap);
  _.unescape = createEscaper(unescapeMap);</pre></div></div>
            
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              <p>Traverses the children of <code>obj</code> along <code>path</code>. If a child is a function, it
is invoked with its parent as context. Returns the value of the final
child, or <code>fallback</code> if any child is undefined.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.result = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj, path, fallback</span>) </span>{
    <span class="hljs-keyword">if</span> (!_.isArray(path)) path = [path];
    <span class="hljs-keyword">var</span> length = path.length;
    <span class="hljs-keyword">if</span> (!length) {
      <span class="hljs-keyword">return</span> _.isFunction(fallback) ? fallback.call(obj) : fallback;
    }
    <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> i = <span class="hljs-number">0</span>; i &lt; length; i++) {
      <span class="hljs-keyword">var</span> prop = obj == <span class="hljs-literal">null</span> ? <span class="hljs-keyword">void</span> <span class="hljs-number">0</span> : obj[path[i]];
      <span class="hljs-keyword">if</span> (prop === <span class="hljs-keyword">void</span> <span class="hljs-number">0</span>) {
        prop = fallback;
        i = length; <span class="hljs-comment">// Ensure we don't continue iterating.</span>
      }
      obj = _.isFunction(prop) ? prop.call(obj) : prop;
    }
    <span class="hljs-keyword">return</span> obj;
  };</pre></div></div>
            
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              <p>Generate a unique integer id (unique within the entire client session).
Useful for temporary DOM ids.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> idCounter = <span class="hljs-number">0</span>;
  _.uniqueId = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">prefix</span>) </span>{
    <span class="hljs-keyword">var</span> id = ++idCounter + <span class="hljs-string">''</span>;
    <span class="hljs-keyword">return</span> prefix ? prefix + id : id;
  };</pre></div></div>
            
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              <p>By default, Underscore uses ERB-style template delimiters, change the
following template settings to use alternative delimiters.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.templateSettings = {
    <span class="hljs-attr">evaluate</span>: <span class="hljs-regexp">/&lt;%([\s\S]+?)%&gt;/g</span>,
    <span class="hljs-attr">interpolate</span>: <span class="hljs-regexp">/&lt;%=([\s\S]+?)%&gt;/g</span>,
    <span class="hljs-attr">escape</span>: <span class="hljs-regexp">/&lt;%-([\s\S]+?)%&gt;/g</span>
  };</pre></div></div>
            
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              </div>
              <p>When customizing <code>templateSettings</code>, if you don’t want to define an
interpolation, evaluation or escaping regex, we need one that is
guaranteed not to match.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> noMatch = <span class="hljs-regexp">/(.)^/</span>;</pre></div></div>
            
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              <p>Certain characters need to be escaped so that they can be put into a
string literal.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> escapes = {
    <span class="hljs-string">"'"</span>: <span class="hljs-string">"'"</span>,
    <span class="hljs-string">'\\'</span>: <span class="hljs-string">'\\'</span>,
    <span class="hljs-string">'\r'</span>: <span class="hljs-string">'r'</span>,
    <span class="hljs-string">'\n'</span>: <span class="hljs-string">'n'</span>,
    <span class="hljs-string">'\u2028'</span>: <span class="hljs-string">'u2028'</span>,
    <span class="hljs-string">'\u2029'</span>: <span class="hljs-string">'u2029'</span>
  };

  <span class="hljs-keyword">var</span> escapeRegExp = <span class="hljs-regexp">/\\|'|\r|\n|\u2028|\u2029/g</span>;

  <span class="hljs-keyword">var</span> escapeChar = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">match</span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-string">'\\'</span> + escapes[match];
  };</pre></div></div>
            
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              <p>JavaScript micro-templating, similar to John Resig’s implementation.
Underscore templating handles arbitrary delimiters, preserves whitespace,
and correctly escapes quotes within interpolated code.
NB: <code>oldSettings</code> only exists for backwards compatibility.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.template = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">text, settings, oldSettings</span>) </span>{
    <span class="hljs-keyword">if</span> (!settings &amp;&amp; oldSettings) settings = oldSettings;
    settings = _.defaults({}, settings, _.templateSettings);</pre></div></div>
            
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              <p>Combine delimiters into one regular expression via alternation.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">var</span> matcher = <span class="hljs-built_in">RegExp</span>([
      (settings.escape || noMatch).source,
      (settings.interpolate || noMatch).source,
      (settings.evaluate || noMatch).source
    ].join(<span class="hljs-string">'|'</span>) + <span class="hljs-string">'|$'</span>, <span class="hljs-string">'g'</span>);</pre></div></div>
            
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              <p>Compile the template source, escaping string literals appropriately.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">var</span> index = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">var</span> source = <span class="hljs-string">"__p+='"</span>;
    text.replace(matcher, <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">match, escape, interpolate, evaluate, offset</span>) </span>{
      source += text.slice(index, offset).replace(escapeRegExp, escapeChar);
      index = offset + match.length;

      <span class="hljs-keyword">if</span> (<span class="hljs-built_in">escape</span>) {
        source += <span class="hljs-string">"'+\n((__t=("</span> + <span class="hljs-built_in">escape</span> + <span class="hljs-string">"))==null?'':_.escape(__t))+\n'"</span>;
      } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (interpolate) {
        source += <span class="hljs-string">"'+\n((__t=("</span> + interpolate + <span class="hljs-string">"))==null?'':__t)+\n'"</span>;
      } <span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (evaluate) {
        source += <span class="hljs-string">"';\n"</span> + evaluate + <span class="hljs-string">"\n__p+='"</span>;
      }</pre></div></div>
            
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              <p>Adobe VMs need the match returned to produce the correct offset.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>      <span class="hljs-keyword">return</span> match;
    });
    source += <span class="hljs-string">"';\n"</span>;</pre></div></div>
            
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              <p>If a variable is not specified, place data values in local scope.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">if</span> (!settings.variable) source = <span class="hljs-string">'with(obj||{}){\n'</span> + source + <span class="hljs-string">'}\n'</span>;

    source = <span class="hljs-string">"var __t,__p='',__j=Array.prototype.join,"</span> +
      <span class="hljs-string">"print=function(){__p+=__j.call(arguments,'');};\n"</span> +
      source + <span class="hljs-string">'return __p;\n'</span>;

    <span class="hljs-keyword">var</span> render;
    <span class="hljs-keyword">try</span> {
      render = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Function</span>(settings.variable || <span class="hljs-string">'obj'</span>, <span class="hljs-string">'_'</span>, source);
    } <span class="hljs-keyword">catch</span> (e) {
      e.source = source;
      <span class="hljs-keyword">throw</span> e;
    }

    <span class="hljs-keyword">var</span> template = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">data</span>) </span>{
      <span class="hljs-keyword">return</span> render.call(<span class="hljs-keyword">this</span>, data, _);
    };</pre></div></div>
            
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              <p>Provide the compiled source as a convenience for precompilation.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>    <span class="hljs-keyword">var</span> argument = settings.variable || <span class="hljs-string">'obj'</span>;
    template.source = <span class="hljs-string">'function('</span> + argument + <span class="hljs-string">'){\n'</span> + source + <span class="hljs-string">'}'</span>;

    <span class="hljs-keyword">return</span> template;
  };</pre></div></div>
            
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              <p>Add a “chain” function. Start chaining a wrapped Underscore object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.chain = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    <span class="hljs-keyword">var</span> instance = _(obj);
    instance._chain = <span class="hljs-literal">true</span>;
    <span class="hljs-keyword">return</span> instance;
  };</pre></div></div>
            
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              <h2 id="oop">OOP</h2>

            </div>
            
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              </div>
              <p>If Underscore is called as a function, it returns a wrapped object that
can be used OO-style. This wrapper holds altered versions of all the
underscore functions. Wrapped objects may be chained.</p>

            </div>
            
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              <p>Helper function to continue chaining intermediate results.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">var</span> chainResult = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">instance, obj</span>) </span>{
    <span class="hljs-keyword">return</span> instance._chain ? _(obj).chain() : obj;
  };</pre></div></div>
            
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              <p>Add your own custom functions to the Underscore object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.mixin = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">obj</span>) </span>{
    _.each(_.functions(obj), <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">name</span>) </span>{
      <span class="hljs-keyword">var</span> func = _[name] = obj[name];
      _.prototype[name] = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
        <span class="hljs-keyword">var</span> args = [<span class="hljs-keyword">this</span>._wrapped];
        push.apply(args, <span class="hljs-built_in">arguments</span>);
        <span class="hljs-keyword">return</span> chainResult(<span class="hljs-keyword">this</span>, func.apply(_, args));
      };
    });
    <span class="hljs-keyword">return</span> _;
  };</pre></div></div>
            
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            <div class="annotation">
              
              <div class="pilwrap ">
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              </div>
              <p>Add all of the Underscore functions to the wrapper object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.mixin(_);</pre></div></div>
            
        </li>
        
        
        <li id="section-189">
            <div class="annotation">
              
              <div class="pilwrap ">
                <a class="pilcrow" href="#section-189">&#182;</a>
              </div>
              <p>Add all mutator Array functions to the wrapper.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.each([<span class="hljs-string">'pop'</span>, <span class="hljs-string">'push'</span>, <span class="hljs-string">'reverse'</span>, <span class="hljs-string">'shift'</span>, <span class="hljs-string">'sort'</span>, <span class="hljs-string">'splice'</span>, <span class="hljs-string">'unshift'</span>], <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">name</span>) </span>{
    <span class="hljs-keyword">var</span> method = ArrayProto[name];
    _.prototype[name] = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">var</span> obj = <span class="hljs-keyword">this</span>._wrapped;
      method.apply(obj, <span class="hljs-built_in">arguments</span>);
      <span class="hljs-keyword">if</span> ((name === <span class="hljs-string">'shift'</span> || name === <span class="hljs-string">'splice'</span>) &amp;&amp; obj.length === <span class="hljs-number">0</span>) <span class="hljs-keyword">delete</span> obj[<span class="hljs-number">0</span>];
      <span class="hljs-keyword">return</span> chainResult(<span class="hljs-keyword">this</span>, obj);
    };
  });</pre></div></div>
            
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        <li id="section-190">
            <div class="annotation">
              
              <div class="pilwrap ">
                <a class="pilcrow" href="#section-190">&#182;</a>
              </div>
              <p>Add all accessor Array functions to the wrapper.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.each([<span class="hljs-string">'concat'</span>, <span class="hljs-string">'join'</span>, <span class="hljs-string">'slice'</span>], <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params">name</span>) </span>{
    <span class="hljs-keyword">var</span> method = ArrayProto[name];
    _.prototype[name] = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">return</span> chainResult(<span class="hljs-keyword">this</span>, method.apply(<span class="hljs-keyword">this</span>._wrapped, <span class="hljs-built_in">arguments</span>));
    };
  });</pre></div></div>
            
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        <li id="section-191">
            <div class="annotation">
              
              <div class="pilwrap ">
                <a class="pilcrow" href="#section-191">&#182;</a>
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              <p>Extracts the result from a wrapped and chained object.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.prototype.value = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>._wrapped;
  };</pre></div></div>
            
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        <li id="section-192">
            <div class="annotation">
              
              <div class="pilwrap ">
                <a class="pilcrow" href="#section-192">&#182;</a>
              </div>
              <p>Provide unwrapping proxy for some methods used in engine operations
such as arithmetic and JSON stringification.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  _.prototype.valueOf = _.prototype.toJSON = _.prototype.value;

  _.prototype.toString = <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-built_in">String</span>(<span class="hljs-keyword">this</span>._wrapped);
  };</pre></div></div>
            
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              <p>AMD registration happens at the end for compatibility with AMD loaders
that may not enforce next-turn semantics on modules. Even though general
practice for AMD registration is to be anonymous, underscore registers
as a named module because, like jQuery, it is a base library that is
popular enough to be bundled in a third party lib, but not be part of
an AMD load request. Those cases could generate an error when an
anonymous define() is called outside of a loader request.</p>

            </div>
            
            <div class="content"><div class='highlight'><pre>  <span class="hljs-keyword">if</span> (<span class="hljs-keyword">typeof</span> define == <span class="hljs-string">'function'</span> &amp;&amp; define.amd) {
    define(<span class="hljs-string">'underscore'</span>, [], <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{
      <span class="hljs-keyword">return</span> _;
    });
  }
}());</pre></div></div>
            
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    </ul>
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